Device for scribing circles



Nov. 29, 1960 R. F. KRIEDER l 2,961,768

DEVICE FOR SCRIBING CIRCLES Filed 001'.. 13. 1959.

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Arrow/5x5 United States Patent O "lee DEVICE FOR SCRIBING CIRCLES Ronald F. Krieder, 231 Smith Ave., Sharon, Pa.

Filed Oct. 13, 1959, Ser. N0. 846,207

1 Claim. (Cl. 33--27) This invention is an improved form of device for describing circles, as for instance upon the blackboard of a school room.

I realize that there have been invented other devices for this same general purpose but the object of my present invention is to provide a comparatively simple form of structure that is capable of performing its intended function in a highly satisfactory manner and that can be manufactured and sold at a comparatively low price.

Other objects will appear from the following description and. claim when considered together with the accompanying drawing. Y

Fig. 1 is a view of my device in position of use, shown partly in section, with the arm indicated in dotted lines in idle position for convenient shipping or storage;

Fig. 2 is an end View of the same;

Fig. 3 is a view taken on line 3-3 of Fig. l;

Fig. 4 is an end view of the device with the arm secured in folded position for shipping or storage;

Fig. 5 illustrates the one-piece stamping from which the chalk-holder is formed.

Referring now to the accompanying `drawing in detail, the hollow aluminum tubing 1 will serve as a housing for the shaft 2 which has its rear end co-axially mounted in the bearing cap 1a pressed into the rear end of the housing 1 and which has its forward end portion 2a of enlarged form extending from the housing 1, so as to be rotatable within the same. The portion 2a of the shaft has an annular shoulder 2b that is engaged by the front end of the housing v1; and the end portion 2a is tapered and carries a rubber tip 3 for centering engagement upon the blackboard B or other surface upon which the circle is to be described.

The shaft 2, which for the most part is of substantially smaller diameter than the inside diameter of the housing 1, is surrounded by a coil spring 4 which has its one end anchored in a hole in the shaft 2 and its other end anchored in the wall of the housing 1.

A cord 5, which is adapted to be wound about the shaft 2, has its one end anchored to the'shaft while its other end extends out through an opening 1b in the housing 1.

Upon the forward enlarged end 2a of the shaft 2 there is mounted the arm 6 so as to extend radially therefrom; and upon this arm there is mounted the holder 7 for the chalk C or other marking element, this holder being adjustable along the length of the arm 6 according to the radius of the circle desired. The arm `6 may be graduated to facilitate determination of the desired radius. This arm may be in the form of an aluminum L with its one side formed with a longitudinal slot 6a to receive the holder 7 for adjustment therealong. This holder may be formed of a single stamping of sheet aluminum of T form with its head part curved into cylindrical form to receive and hold the chalk or other marker, the parallel ends of this holder portion being held together by the screw and nut 8; and the leg portion 7a of this holder blank is bent back upon itself so as to be slidable along and clamped upon the arm 6 in adjusted position by 2,961,768 Patented Nov. 29, 1960 means of the wing nut 9 on the screw 9a through the slot 6a of the arm 6.

The hinge connection 10 for the arm 6 permits it to be folded back against the housing 1 to collapsed position for shipping or storage during periods of non-use. The arm 6 may be held in such folded position by any suitable means as for instance by engagement of the hook 6b in the slot 6a of the arm 6, this hook being mounted in the eye member 6c secured to the cap 1a. The arm 6 is normally forced towardsV operative position and is pressed against the surface B by the spring 11 which is anchored at its one end in the arm 6 and at its other end in the forward end portion 2a of the shaft 2. With this arrangement, the arm 6 will assume proper position for different lengths of chalk or other marking element upon applying the device to position of use.

Having moved the chalk holder along the arm 6 and secured the same in proper position according to the radius of circle desired at any given time, the operator will hold the housing 1 in his one hand with the tip 3 occupying position upon the surface B so as to locate the center of the circle to be described, and he will then pull the cord 5 so as to rotate the shaft 2 and the arm 6, with the result that the chalk or other marker will be rotated about the tip 3 as a center and will thus describe a circle upon the surface B. Upon release of the cord 5, it Will be re-wound about the shaft 2 by the spring 4.

If so desired, the cord 5 may lirst be pulled out so as to place the spring 4 under tension and to rotate the arm 6 about its center before placing the device in position of use; then, upon placing the device in operative position and releasing the cord 5, the arm and its marker will describe the circle upon the surface B by force of the spring 4 that was placed under tension by the initial turning of the shaft by pulling the cord 5, as just explained. Thus the describing of the circle may be effected by either the winding or re-winding of the cord 4. p

From the above it will be seen that I have devised a simple form of structure that is capable of performing its intended function in an effective and dependable manner and in which the main operating parts are housed within the tubing 1 so as to be protected. This device may be made of other materials than that herein mentioned, there may be provided other forms of chalk-holder, and the winding spring 4 may be anchored in other manners than that herein described; it being understood that the present form of disclosure is merely for the purpose of illustration and that there might be devised various other forms of structure without departing from the spirit of my invention as herein set forth and claimed.

What I claim is:

A circle scribing device comprising a tubular housing open at its one end and having a fixed bearing means in its other end, a single continuous shaft having its one end rotatably mounted in said bearing means and having its other end extending from and having engagement with the open end of said housing so as to be co-axially rotatable therewith, a spring member attached at its ends to said shaft and housing, respectively, so as to provide rotary tension for said shaft, acord attached to said shaft and extending out through said housing so as to serve as a means for placing said spring means under tension, an arm attached to the extending end of said shaft and extending radially therefrom, and means for mounting a marking element upon said arm.

References Cited in the le of this patent UNITED STATES PATENTS 951,255 McMurray Mar. 8, 1910 1,143,531 Giese June 15, 1915 2,266,865 Herrington Dec. 23, 1941 

